FR3045501A1 - WHEEL TRAIN OF A VEHICLE - Google Patents

Abstract

The invention relates to a vehicle wheel train, particularly automobile. The invention is characterized in that the first wedge (6) is elastically deformable in a longitudinal direction relative to the vehicle with a relatively low linear stiffness and the second wedge (7) is also elastically deformable in this longitudinal direction and has a nonlinear stiffness in transverse and longitudinal directions increasing from low longitudinal stresses to strong longitudinal stresses applied to the corresponding half-train (1), allowing the suspension arm (4) of each half-train (1) to be movable in translation in the longitudinal direction and movable in rotation about an axis perpendicular to the longitudinal and transverse directions passing on a pivot point centered on the first wedge (6). The invention finds its application in the field of the automotive industry.

Description

The invention relates to a wheel train of a vehicle, in particular a motor vehicle.

The invention applies in particular, but in a non-limiting manner, to a motor vehicle comprising at least one front wheel drive wheel type pseudo MacPherson.

It is well known to integrate this type of wheel train consist of two half-trains. Each half-train comprises a triangular suspension arm pivotally connected by one of its vertices, for example via a ball joint, to a stub axle of the wheel of the half-train. The other two vertices of the triangular suspension arm of each half-train are connected to the chassis of the vehicle. This suspension arm has the function of making the steering firm and robust by stabilizing the wheel of the half-train. A major disadvantage of such a configuration is the transmission to the wheel set of all the vibrations induced for example by the periodic excitations of the wheel, the acyclisms of the engine, or the percussions and other excitations of smaller amplitude coming from the imperfections of the road.

To overcome this drawback, it is known from US patent application 2005/0051987 to use a deformable wedge positioned at the point of connection between a top of the triangular suspension arm of each half-train of a train pseudo MacPherson and the chassis of the vehicle. This document describes in particular a wedge deformable in a direction transverse to the direction of movement of the vehicle inducing a rotational movement of the suspension arm of each half-train around a pivot centered on the other vertex connected to the frame of the arm of suspension. In addition, the stiffness of this wedge is asymmetrical, so that its deformation is less amplified in acceleration than during braking. This results in a filtration of a part of the perceived vibrations and an improvement of vibratory comfort.

However, such a deformable wedge structure has few degrees of freedom, which ultimately does not offer a large latitude of movement to the triangular suspension arm. In fact, a large part of the vibrations are not filtered. The vibratory comfort is therefore perfectible.

The present invention aims to overcome the above drawbacks of the prior art, while providing optimum vehicle handling in different driving situations that may be encountered by the driver of the vehicle.

To achieve this object, the invention relates to a MacPherson type pseudo train of a vehicle of which each half-train comprises a generally triangular suspension arm ensuring the guidance of the plane of the wheel of the half-train, a the top of the suspension arm being pivotally connected to a knuckle of the corresponding half-gear wheel, the two other vertices of the suspension arm of each half-train being hingedly connected to the chassis of the vehicle respectively via first and second elastically deformable wedges, the second wedge located furthest back from the direction of travel in the forward direction of the vehicle being deformable in a direction transverse to the vehicle, characterized in that the first wedge is elastically deformable in a longitudinal direction relative to the vehicle with relatively low linear stiffness and the second hold is also lastically deformable in this longitudinal direction and has a nonlinear stiffness in transverse and longitudinal directions increasing from low longitudinal stresses to strong longitudinal stresses applied to the corresponding half-train, allowing the suspension arm of each half-train to be mobile in translation in the longitudinal direction and mobile in rotation about an axis perpendicular to the longitudinal and transverse directions passing on a pivot point centered on the first wedge.

According to another feature, the shims of each suspension arm allow the filtering of vibration frequencies that can be transmitted to the corresponding half-gear wheel greater than or equal to 15 Hz.

According to another feature, the linear stroke in the transverse direction of the second shim of the suspension arm of each half-train is greater than the linear stroke in the longitudinal direction of the second shim.

According to another feature, the stiffness in the longitudinal direction of the first shim of the suspension arm of each half-train is selected from values between half and triple the stiffness along the longitudinal direction of the second shim from the same suspension arm.

According to another feature, the first shim of the suspension arm of each half-train is shaped cylindrical ring with its longitudinal axis of symmetry oriented parallel to the longitudinal direction of the vehicle.

According to another feature, the second shim of the suspension arm of each half-train is shaped cylindrical ring with its longitudinal axis of symmetry oriented perpendicularly to the longitudinal and transverse directions of the vehicle.

In another feature, the stiffness in the transverse direction of the wedge portions located on either side of the axis of symmetry of the second shim are different.

In another feature, the linear races in the longitudinal direction of the wedge portions located on either side of the axis of symmetry of the second wedge are different.

The invention also relates to a vehicle, including an automobile, comprising a drive train as described above.

In another feature, the drive train is the front axle.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows with reference to the accompanying drawings given solely by way of example illustrating a embodiment of the invention and in which: - Figure 1 shows the half-train seen in perspective of a front axle according to the invention, located to the right of the vehicle relative to the direction of travel in the forward direction of the vehicle; FIG. 2 represents an elevational view of the suspension arm of the half-train of FIG. 1, the arrows illustrating the movement of the wedges and the suspension arm in the case of longitudinal loading of the acceleration type with respect to the direction of travel in motion; front of the vehicle; - Figure 3 shows a view similar to that of Figure 2, the arrows illustrating the movement of the wedges and the suspension arm in case of braking type longitudinal stress relative to the direction of travel in the forward direction of the vehicle; - Figure 4 is an enlarged view along the arrow IV of Figure 1 of the second shim of the suspension arm of the half-train; FIG. 5 represents two curves showing the evolution of the stiffness of the second shim of a suspension arm respectively of the prior art and of the invention as a function of the amplitude of displacement of this shim in a longitudinal direction. in relation to the direction of travel in the forward direction of the vehicle; FIG. 6 represents two curves showing the evolution of the stiffness of the second wedge respectively of the prior art and of the invention as a function of the displacement amplitude of this wedge in a direction transverse to the direction of displacement. in the forward direction of the vehicle.

The invention is described below with reference to Figures 1 to 6, applied to a vehicle, including automotive.

This vehicle comprises a drive train, preferably the front axle, comprising two half-trains 1 each carrying a wheel of the vehicle, only the half-gear 1 positioned to the right relative to the direction of travel in the forward direction of the vehicle being shown in FIG.

This half-train 1 comprises a damper 2 secured to a rocket carrier 3, which is intended to support a rocket (not shown) of the half-train 1, this rocket being intended to be associated with the wheel of the half -train 1.

The half-train 1 also comprises a triangular-shaped suspension arm 4 pivotally connected by one of its vertices S1 to one end of the stub axle 3. Preferably, the top S1 of the suspension arm 4 is connected. to the knuckle through a ball joint 5.

The other two vertices S2, S3 of the suspension arm 4 are connected to the vehicle frame articulated via respectively first 6 and second 7 elastically deformable shims.

The first shim 6 is in the form of cylindrical ring integral with the top S2 of the suspension arm 4, and has its longitudinal axis of symmetry substantially parallel to a longitudinal direction relative to the vehicle. The first shim 6 is deformable in this longitudinal direction, and its longitudinal axis of symmetry is likely to shift a few degrees around the longitudinal direction of the vehicle depending on the forces applied at the top S2 of the suspension arm 4.

The second shim 7, located furthest back from the direction of travel of the vehicle in forward direction, has a generally cylindrical shape and has its longitudinal axis of symmetry substantially perpendicular to the longitudinal direction of the vehicle and a transverse direction compared to the vehicle. The second wedge 7 is elastically deformable in these longitudinal and transverse directions relative to the vehicle, and its longitudinal axis of symmetry is likely to shift a few degrees around this direction perpendicular to the longitudinal and transverse directions of the vehicle, depending on the forces applied. at the top S3 of the suspension arm 4.

The elastic deformability of each shim 6, 7 of the suspension arm 4 allows the suspension arm 4 of the half-train 1 to be movable in translation in the longitudinal direction of the vehicle, and mobile in rotation about an axis perpendicular to the longitudinal and transverse directions of the vehicle, this axis passing over a pivot point P centered on the vertex S2 comprising the first wedge 6.

The first shim 6 has a linear stiffness, that is to say that the value of the stiffness of the first shim 6 increases with the amplitude of deformation in the longitudinal direction of the first shim 6 according to an affine function. The amplitude of longitudinal deformation of the first shim 6 is all the greater as the longitudinal stresses applied to the corresponding half-gear 1 are large.

By way of example, the value of the stiffness of the first shim 6 is between 50 and 70 decaNewton per millimeter (daN / mm), preferably around 60 daN / mm, even more preferentially of the order of 63 daN / mm. The stiffness of the first shim 6 according to the invention is lower than the stiffness of this type of wedge used in the state of the art, which usually have a stiffness around 1000 to 2000 daN / mm. The translation movements in the longitudinal direction of the suspension arm 4 of the half-train 1 according to the invention are thus facilitated.

The second shim 7 has a nonlinear stiffness. Indeed, the stiffness in transverse and longitudinal directions of the second wedge 7 increases from small amplitude of deformation of the wedge 7 to high amplitudes of deformation of the wedge 7. The distortion amplitudes respectively longitudinal and transverse the second shim 7 are larger than the longitudinal and transverse stresses applied to the corresponding half-train 1 are large.

The nonlinear behavior of the stiffness of the second wedge 7 results in a very gradual increase in stiffness in response to low longitudinal and / or transverse stresses of the corresponding half-train 1, then by an increase in stiffness more and more rapidly until saturation as these stresses applied to the corresponding half-train 1 increase. In addition, the second wedge 7 is asymmetrical, which means that the stiffness of the second wedge 7 also depends on the direction of deformation of the second wedge 7. In particular, the linear stroke of the second wedge 7 in the transverse direction is greater than the linear stroke of the same shim 7 in the longitudinal direction.

The behavior of the shims 6, 7 and the consequences on the behavior of the suspension arm 4 and the corresponding half-train 1 will be specified later in the description.

The structure of the second shim 7 will now be described with reference to FIG. 4.

The second shim 7 comprises a rigid cylindrical outer ring 9 secured to the third metal top S3 of the suspension arm 4, and a rigid cylindrical inner metal ring 8 secured to the chassis of the vehicle by means of a fixing screw. The second shim also comprises an elastically deformable cylindrical body 10, for example made of elastomeric material, positioned between the two rigid cylindrical rings 8, 9. The deformable body 10 comprises four cavities 11, 13, 15, 16 extending longitudinally to the cylindrical body deformable 10, these cells being positioned in pairs on either side of the inner cylindrical ring 8, diametrically opposed.

One of the four cells 13 has a substantially chevron-shaped cross section oriented towards the axis of symmetry of the second wedge 7. Another of the four cells 11 has a different section, substantially curved and oriented towards the axis of symmetry of the second wedge 7, so that the second wedge 7 is asymmetrical in the longitudinal direction of the vehicle. In addition, the cells 11, 13 are aligned in the longitudinal direction of the vehicle.

The other two cells 15, 16 are aligned in the transverse direction of the vehicle and have cross sections of different shape. The cell 15, which is the one positioned to the right with respect to the direction of movement of the vehicle in the forward direction, has a substantially chevron-shaped cross section oriented towards the axis of symmetry of the second wedge 7. The other cell 16 has a cross section in the form of an ear. In addition, a longitudinal lug 17 is integral with the deformable body 10 and serves to reduce the stiffness of the second shim 7 at the start of the race. The two wedge portions situated on either side of the inner cylindrical ring 8 thus have stiffnesses in the different transverse direction once the linear stroke has been consumed.

Although not shown, the first shim 6 comprises two concentric cylindrical metal rings respectively integral with the top S2 and the chassis of the vehicle, and a cylindrical body of deformable material, for example elastomer, fixed between the two cylindrical rings.

The behavior of the half-train 1 of Figure 1 according to the solicitations applied to the latter will now be described.

Each half-train 1 provided shims 6, 7 described above is intended to absorb the shocks associated with longitudinal and transverse stresses applied to the half-train 1, as previously exposed in part.

These transverse and longitudinal stresses relative to the vehicle may be weak or strong. Low stresses may correspond to moderate acceleration of the vehicle, for example accelerations when a high speed ratio is engaged, or moderate decelerations of the vehicle, for example due to engine braking. Finally, the defects and unevenness of the road, related for example to potholes, road connections or manholes, also cause low stresses on the half-gear 1 of wheels, even if the vehicle is moving at a constant speed . It is considered that the low stresses correspond to an absolute value of force exerted on the wheel of the half-train 1 less than or equal to about 100 daN in a longitudinal direction relative to the vehicle.

Beyond 100 daN, we speak of strong stresses, caused for example by a strong acceleration of the vehicle when a low speed ratio is engaged, or by a strong deceleration for example due to a sudden braking by the driver of the vehicle. vehicle.

In a first step, the behavior of the half-train 1 as a function of stresses due to accelerations A will now be described, with reference to FIGS. 2, 5 and 6.

Under these conditions, the suspension arm 4 of the half-train 1 has a composite motion, firstly in translation in the longitudinal direction of the vehicle in the direction of the negative X according to the reference of Figure 2 as shown by the arrows T1, that is to say forward with respect to the direction of travel in the forward direction of the vehicle, and secondly in rotation in the counterclockwise direction along an axis Z perpendicular to the longitudinal and transverse directions of the vehicle, passing at the pivot point P of the top S2 of the suspension arm 4, as represented by the arrow R1. Of course, this movement of the suspension arm 4 is valid for a half-train 1 as shown in Figure 1, that is to say positioned to the right with respect to the direction of travel of the vehicle forward. For a half-train positioned to the left, the rotation of the suspension arm 4 will therefore be in the clockwise direction in case of stresses due to acceleration of the vehicle.

The translation movement of the suspension arm is made possible by the deformation in the longitudinal direction of the vehicle along the positive X of the first shim 6 of the suspension arm 4.

The rotational movement is made possible by the deformation of the second wedge 7 in both longitudinal and transverse directions of the vehicle, respectively according to the negative X and positive Y of the reference shown in Figure 2.

Figures 5 and 6 show the displacement of the outer cylindrical ring 9 of the second wedge 7 relative to its axis of symmetry, respectively in the longitudinal direction and in the transverse direction of the vehicle. These displacements Cx, Cy are due to the deformation of the elastically deformable body 10 in response to the transverse and longitudinal stresses F applied to the half-train. The continuous curves 19, 21 respectively of FIGS. 5 and 6 represent the displacements Cx, Cy of the outer cylindrical ring 9 of the second wedge 7 with respect to its axis of symmetry as a function of the force applied to the wheel of the half-train. 1 corresponding, respectively in the longitudinal and transverse directions of the vehicle. The discontinuous curves 18, 20 represent these same displacements for a wedge of the prior art positioned at the level of the crown S3 of a suspension arm 4.

It appears in Figure 5 that for low longitudinal stresses, the longitudinal movement Cx of the second shim 7 of the half-train 1 according to the invention is more important than the longitudinal movement of a shim of the art prior. The stiffness of the second shim 7 according to the invention, in the longitudinal direction of the vehicle, has an almost linear behavior for longitudinal stresses applied to the wheel of the half-train 1 less than 100 daN. This stiffness is of the order of 40 to 50 daN / mm, preferably about 46 daN / mm, for a displacement Cx of the outer cylindrical ring 9 of the wedge 7 between 0 and 1.5 mm, according to the reference shown in FIG. 2. This value is indeed relatively small compared to the stiffness of a shim of the prior art, which is of the order of 190 daN / mm.

Thus, the half-train 1 of the invention allows efficient filtering of the vibrations that can be transmitted to the wheel half-train and whose frequency is greater than 15 Hz. The half-train 1 then acts as a low-pass filter when the latter is subjected to low longitudinal stresses, which results in a strong attenuation of these vibrations which has a direct positive impact on driving comfort.

In addition, with reference to Figure 6, it appears that the second shim 7 according to the invention is also more flexible for low transverse stresses relative to the wedge of the prior art. Thus the transverse movement Cy of the second wedge 7 of the half-train 1 according to the invention is more important than the transverse movement of a wedge of the prior art. It will also be noted that for a transverse stress of the order of 100 daN, the displacement Cy of the outer cylindrical ring 9 of the second wedge 7 is of the order of 2.5 mm in the direction of the positive Ys according to the reference shown in FIG. 2, more important than the longitudinal displacement Cx for similar constraints applied to the vertex S1.

For stronger acceleration urges, greater than 100 daN, it is noted in Figures 5 and 6 that the stiffness respectively along the longitudinal and transverse directions of the second wedge 7 saturate quickly to join values of stiffness close to zero. prior art, so as to ensure a high stability of the half-train 1.

The behavior of the half-train 1 as a function of stresses due to decelerations will now be described, with reference to FIGS. 3, 5 and 6. Under these conditions, the suspension arm 4 of the half-train 1 presents a composite movement, on the one hand in translation along the longitudinal direction in the direction of the positive Xs according to the reference of FIG. 3 as represented by the arrows T2, that is to say, forward with respect to the direction of movement in forward of the vehicle, and secondly in rotation in the clockwise direction along an axis Z perpendicular to the longitudinal and transverse directions of the vehicle passing on the pivot point P of the top S2 of the suspension arm 4, as represented by the arrow R2 . Of course, this movement of the suspension arm 4 is valid for a half-train 1 as shown in Figure 1, that is to say positioned to the right with respect to the direction of travel of the vehicle forward. For a half-train positioned to the left, the rotation will be done in the counterclockwise direction in case of stress due to decelerations.

The translation movement of the suspension arm is made possible by the deformation in the longitudinal direction along the positive X of the first shim 6 of the suspension arm.

The rotational movement is made possible by the deformation of the second wedge 7 in its two longitudinal and transverse directions respectively along the positive X and the negative Y of the reference shown in Figure 3.

It appears in FIG. 5 that the evolution of the absolute value of the stiffness along the longitudinal direction of the second wedge 7 in the direction of the negative X's is different from the revolution of this stiffness observed in the direction of the positive X's. , which reflects the asymmetry of the second shim 7 in the longitudinal direction, and a different behavior of the second shim 7 in this direction as well in response to deceleration solicitations D as acceleration solicitations A applied corresponding half-train 1: in particular, the longitudinal stroke of the shim is greater in deceleration than acceleration for the same effort felt by the suspension arm 4.

With reference to FIG. 6, it appears that the second wedge 7 according to the invention has a stiffness which increases more rapidly for transversal stresses according to the negative Y's, that is to say in deceleration, than for transversal stresses according to the positive Y, that is to say in acceleration. This reflects the dissymmetry of the second shim 7 in the transverse direction. In addition, for decelerating stresses, the curves 20, 21 of FIG. 6 clearly illustrate that the stiffness of the second shim 7 according to the invention saturates much more and faster than the stiffness of a wedge of the prior art. positioned in S3 of the suspension arm 4. This brings even more stability to the half-train 1 during strong decelerations, greater than 100 daN in absolute value.

Finally, to allow the reduction of the dimensions of the second shim 7, the stiffness in the longitudinal direction of the first shim 6 of the suspension arm 4 of each half-train 1 is between half and triple of the stiffness in the longitudinal direction of the second shim 7 of the same suspension arm 4. In this way, the forces experienced by the suspension arm 4 when the half-train 1 is subjected to longitudinal stresses are well distributed between the two shims 6 , 7.

Thus, the half-train 1 according to the invention is able to filter a major part of the vibrations that can be transmitted to the wheel of the half-train 1, when the latter is subjected to transverse and especially longitudinal stresses small amplitudes. The result is optimized driving comfort. In addition, the non-linear behavior of the second shim 7 of the suspension arm 4 of the half-train 1 ensures its stability when it is subjected to loads of high amplitude.

The configuration as described is not limited to the embodiment as described above. It has been given only as a non-limiting example. Multiple modifications can be made without departing from the scope of the invention. Thus, one could provide a first shim 6 whose axis of symmetry is oriented in a direction substantially perpendicular to the transverse and longitudinal directions of the vehicle, and a second shim 7 whose axis of symmetry is substantially parallel to the longitudinal direction of the vehicle . One could also provide that the axes of symmetry respectively of the two shims 6, 7 are oriented in the same direction.

Claims (10)

1. MacPherson type pseudo train of a vehicle, in particular an automobile, of which each half-train (1) comprises a suspension arm (4) of generally triangular shape for guiding the plane of the wheel of the half-train (1). , a top (S1) of the suspension arm (4) being pivotally connected to a knuckle (3) of the wheel of the half-gear (1) corresponding, the two other vertices (S2, S3) of the arm of suspension (4) of each half-train (1) being hingedly connected to the chassis of the vehicle via respectively first and second resiliently deformable wedges (6, 7), the second wedge (7) located furthest back from the direction of travel in the forward direction of the vehicle being deformable in a direction transverse to the vehicle, characterized in that the first wedge (6) is elastically deformable in a longitudinal direction relative to the vehicle having a relatively low linear stiffness and the d the second wedge (7) is also elastically deformable in this longitudinal direction and has a nonlinear stiffness in transverse and longitudinal directions increasing from low longitudinal stresses to strong longitudinal stresses applied to the corresponding half-train (1), allowing the suspension arm (4) of each half-train (1) to be movable in translation in the longitudinal direction and mobile in rotation about an axis perpendicular to the longitudinal and transverse directions passing on a pivot point centered on the first hold (6). 2. Train according to claim 1, characterized in that the wedges (6, 7) of each suspension arm (4) allow the filtering of the vibration frequencies that can be transmitted to the wheel of the half-train (1) corresponding greater than or equal to 15 Hz. 3. Train according to claim 1 or 2, characterized in that the linear stroke in the transverse direction of the second shim (7) of the suspension arm (4) of each half-train (1) is larger than the linear stroke in the longitudinal direction of this second wedge (7). 4. Train according to any one of claims 1 to 3, characterized in that the stiffness in the longitudinal direction of the first shim (6) of the suspension arm (4) of each half-train (1) is selected from values between one half and one third of the stiffness in the longitudinal direction of the second shim (7) of the same suspension arm. 5. Train according to any one of claims 1 to 4, characterized in that the first shim (6) of the suspension arm (4) of each half-train (1) is shaped cylindrical ring with its longitudinal axis of symmetry oriented parallel to the longitudinal direction of the vehicle. 6. Train according to any one of claims 1 to 5, characterized in that the second shim (7) of the suspension arm (4) of each half-train (1) is cylindrical ring-shaped with its longitudinal axis of symmetry oriented perpendicular to the longitudinal and transverse directions of the vehicle. 7. Half-train according to claim 6, characterized in that the linear races in the transverse direction of the wedge portions located on either side of the axis of symmetry of the second wedge (7) are different. 8. Half-train according to claim 6 or 7, characterized in that the linear races in the longitudinal direction of the wedge portions located on either side of the axis of symmetry of the second wedge (7) are different. 9. Vehicle, especially automobile, comprising a drive train according to any one of claims 1 to 8. 10. Vehicle according to claim 9, characterized in that the drive train is the front axle.